Optical Properties and Reliability Studies of Gradient Alloyed Green Emitting (CdSe)x(ZnS)1-x and Red Emitting (CuInS2)x(ZnS)1-x Quantum Dots for White Light-Emitting Diodes

Luminescent materials become one of interesting issues for white LED-based lighting devices (WLEDs) due to their high performances for converting the monochromatic light from UV/blue LED chips into white light. Nevertheless, the availability of rare earth materials, the low color rendering index (CRI) and too-cold color temperature of the white LEDs remain some drawbacks to penetrate into the general LED lighting markets. Herein, we report the development of rare-earth-free luminescent nanocomposites combined with a UV/blue LED chip in order to provide white light. Gradient alloyed cadmium selenide/zinc sulfide (CdSe)(x)(ZnS)(i-x) and copper indium sulfide/zinc sulfide (CuInS2)(x)(ZnS)(1-x) quantum dots have been used to achieve the luminescent nanocomposite films in silicone as polymer matrix. The optical performances were investigated upon LED excitation. The photometric parameters of systems consisting of luminescent nanocomposites and LEDs including color rendering index (CRI), correlated color temperature (CCT), Commission Internationale de l'Eclairage (CIE) chromaticity coordinates, and luminous efficacy can be tuned by controlling the compositions and thickness of nanocomposite films. Furthermore, the thermal stability and the reliability of these luminescent nanocomposite films were investigated.